Light does not travel in straight lines. It bends. This is what we have been trying to tell you all along.
We are talking about two different things. Light will bend in a medium. It will bend in a medium like water, clouds, glass. it is called refraction. Here is the definition.
Refraction is essentially a surface phenomenon. The phenomenon is mainly in governance to the law of conservation of energy and momentum. Due to change of medium, the phase velocity of the wave is changed but its frequency remains constant.
What was proven in the 1920 test was the light in NO medium like space can be bent by gravity alone.